Electric timepiece drive with cut-off



United States Patent 3,500,103 ELECTRIC TlMEPlECE DRIVE WITH CUT-OFFRoger S. Swain, Wolcott, and Gerald R. Wootton,

Thomaston, Conn., assignors to Benrus Corporation, a corporation ofDelaware Filed Dec. 7, 1966, Ser. No. 599,860 Int. Cl. H02p 7/00 US. Cl.313-138 19 Claims ABSTRACT OF THE DISCLOSURE still present.

The present invention relates to an electric drive for a timepiece orthe like in which the timepiece indication is advanced sequentially by aseries of sequential signals and in which the powered energization ofthe drive is cut off when the desired indication advance has been madewhether the initiating sequential signal is still in existence or not.

A major problem involved in battery-energized timepieces, andparticularly watches, is the length of time that such timepieces willcontinue to operate satisfactorily before the battery has to be replacedor recharged. The smaller the timepiece, and hence the smaller thebattery which can be used therewith, the more critical doe this problembecome. It is therefore of vital importance to improve the efficiency ofoperation of the timepiece driving mechanism to as great a degree aspossible, thereby to reduce the power consumption thereof and thuscorr'espondingly increase the battery lifetime under operatingconditions.

In the usual type of battery-powered timepiece the time indication means(conventionally a set of hands movable over a dial) is driven instep-by-step manner by a series of accurately timed sequentiallyrecurrent signals, each signal being effective to advance the indicatingmechanism by one step. The signals are effective to cause theenergization of a driving means operatively connected to the hands orother indicating mechanism, and the movement of the hands by the drivingmeans constitutes the major mechanical work performed by the timepiece.In order that this work should be performed it is necessary that thedriving means be appropriately electrically powered, and the electricpower thus provided to the driving means constitutes one of the majorfactors constituting the drain of electrical energy from the energizingbattery. It therefore is desirable to limit the energization of thedriving means only to that period of time which is required for it toperform its assigned task; any energization of the driving means afterthat assigned task has been performed represents a waste of energy.

Attempts to control the duration of energization of the driving means bycontrolling the duration of the recurrent control signals are noteffective. With such an approach the control signals must, for safetyssake, have a duration somewhat longer than the maximum time required tomove the indicating mechanism through a given step. If that were notdone the indicating mechanism might under some operating circumstancesfail to be moved properly, with consequent loss in accuracy. The safetyfactor which must be provided represents a con- 3,500,103 Patented Mar.10, 1970 stant unnecessary drain on the battery. Moreover, the length oftime required for the indicating mechanism to move through a given stepmay vary widely with different ambient conditionsthe indicated movementmay be more rapid at higher temperatures than the lower temperatures, orwith the Watch incertain orientations rather than in other orientations.When the signal duration is designed to take care of the slowestmovement rate for the indication means, as it must if the timepieceaccuracy is to be maintained, operation of the watch on those occasionswhen the indication means moves more freely and rapidly will result inunnecessary power consumption.

It is the prime object of the present invention to devise an electricdrive for a timepiece or the like which avoids the above disadvantages,and which in particular achieves a very high degree of electricalefficiency by energizing the driving means for the indicator only forthat period of time necessary at any given instant to cause theindicator to move in a predetermined fashion, the energization of thedriving means thereafter being cut off whether or not the control signalis still in existence. Such a system not only ensures that driving poweris applied only for those periods of time when it is really required,thereby reducing current drain and lengthening the effective life of theenergizing batteries, but it also permits the use of control signals ofsimplified character, thereby minimizing the complexity of the circuitryrequired to produce such control signals and correspondingly reducingthe size and cost, and increasing the reliability of the overallelectronic circuitry involved.

These results are accomplished by causing the control signal to energizethe driving means for the indicator, producing the desired movement ofthe indicator, and teranimating the energization of the driving means assoon as the desired step operation of the driving means has been sensedby appropriate sensing means. The cutting off of the energization of thedriving means in that fashion is accomplished independently of theinitial signal, whether it is still in existence or not. Once theenergization of the driving means has been thus cut off, the circuitryis immediately readied to repeat the cycle of energization and cut-offas soon as the next control signal is received. The sensing means cansense any desired parameter of the action of the indicator or the movingmeans therefor.'For example, it can sense when the output member hasmoved a predetermined distance or when the output member has achieved apredetermined velocity of movement.

To the accomplishment of the above, and to such other objects as mayhereinafter appear, the present invention relates to an electric drivesystem for a time piece or the like, as defined in the appended claimsand as described in this specification, taken together with theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram representation of the system of thepresent invention;

FIG. 2 is a schematic representation of one type of mechanical drive andsensing means which can be employed;

FIG. 3 discloses another type of driving and sensing means which can beemployed;

FIG. 4 is a circuit diagram of the control means, mechanical drive andcut-off means designed for terminating energization of the mechanicaldrive after the output member of the latter has achieved a predeterminedvelocity of movement;

FIG. 5 is a circuit diagram of a system similar to FIG. 4 but designedto terminate energization of the mechanical drive after the outputmember thereof has moved a predetermined distance; and

FIGS. 6A-E are graphical representations, on the same time scale, ofdifferent parameters of the system of FIG. 4, FIG. 6A representing inputsignals the time duration of which is in excess of that required toachieve the predetermined movement of the output member, FIG. 6Brepresenting the input signal of FIG. 6A after having beendifferentiated, FIG. 6C representing the sensing signal output from thesensing coil, FIG. 6D representing the driving or power current, andFIG. 6E representing the movement of the indicator.

As is schematically disclosed in FIG. 1, the timepiece comprises anindicator means generally designated A which, conventionally, comprisesa dial 2 over which minute and hour hands 4 and 6 move, the latter beingdriven in accurately timed fashion by a mechanical drive means generallydesignated B. The present invention relates to a mechanical drive meansB which is electrically energized, but the precise nature of themechanical drive means B, and the precise nature of the indicator meansA, form no direct part of the present invention, and may be widelyvaried. A control means generally designated C is operatively connectedto the mechanical drive means B so as to energize the latter and causecorresponding movement of the indicator means A each time that a signalis received from the timed signal source generally designated D. Theprecise nature of the time signal source D forms no part of the presentinvention, and it, too, may be widely varied, provided only thatproduces an output of timed signals each of which is designed toinitiate or cause the initiation of a predetermined movement of theindicator means A. Operatively connected between the mechanical drivemeans B and the control means C is a cut-off means generally designatedE. The cut-ofi" means senses the output of the mechanical drive means B,and when that output has achieved a predetermined status, such as agiven amount of mechanical translation or a given speed of translation,it acts on the control means C so as to terminate the energization ofthe mechanical drive means B even though the signal from the source Dmay still be active. Indeed, in order to make the energization of themechanical drive means B entirely independent of the time duration ofeach signal from the source D, so that the output of the mechanicaldrive means B will attain ints predetermined character whether theinitiating signal has prematurely disappeared or remains in existencelonger than desired, the control means C is designed to be affected bythe signal from the source D only when that signal is first received,the control means C then causing energization of the mechanical drivemeans D continuously until the cut-off means E becomes operativelyactive thereupon.

FIGS. 2 and 3 illustrate, in semi-schematic form, two exemplary types ofdrives for the indicator A, and illustrate the manner in which themechanical drive is actuated and the sensing for the cut-off means isaccomplished.

In FIG. 2 the hour and minute hands 6 of the indicator A are designed tobe driven by a rotor 8 having magnetizable teeth 10 formed on theperiphery thereof. A magnetic pole piece 12 is fixedly mounted adjacentthe periphery of the rotor 8 and is provided with a winding or coil 14.Each time that the coil 14 is energized a rotor tooth 10, thenrotationally displaced therefrom by the angle x, is drawn intoregistration therewith. Subsequent de-energization of the coil 14permits the rotor 8 to rotate further until the next suceeding rotortooth 10 moves into position displaced from the pole piece 12 by theangle x (or else a pair of appropriately positioned and rotationallystaggered pole pieces 12 and coils 14 are alternately energized). Uponthe next energization of the coil 14 the said succeeding rotor tooth 10is moved into registration with the pole piece 12, and so on, thusproducing an essentially conventional step-by-step rotational movementof the rotor 8. A second pole piece 16 on which coil 18 is wound is alsofixedly positioned in electromagnetic relationship with the rotor teeth10, and when a given tooth 10 is moved into registration with the polepiece 12 another tooth 10, initially displaced from the pole piece 16 byan angle y, moves into registration with or past the pole piece 16,thereby electromagetically inducing a voltage in the winding 18, saidvoltage being representative of the position and velocity of the rotor8.

In FIG. 3 a ratchet wheel 20 is rotated in step-by-step fashion by meansof a pawl 22 mounted on arm 24, the latter being operatively connectedto armature 26 of an electromagnet generally designated 28 andcomprising a support 29.having central passage 31 through which thearmature 26 is slidable. The support 29 carries on its exterior thewindings or coils 14 and 18, arranged in axially spaced relationship.The armature 26 normally assumes a position to the left as shown in FIG.3 (as through the action of a biasing spring, not shown, thereon), inwhich position its right hand end is outside the coil 18. When the coil14 is energized the armature 26 is pulled to the right, thus advancingthe ratchet wheel 20 one step. During this movement the right hand endof the armature 26 enters the coil 18, inducing a voltage therein which,similar to the embodiment of FIG. 2, is representative of the positionand velocity of the pawl 22. When energization of the winding 14 isterminated any appropriate means, such as the biasing spring (not shown)previously mentioned, returns the armature 26, and with it the arm 24and pawl 22, to original position as illustrated in FIG. 3. Thus hereagain an essentially conventional stepwise rotation of the ratchet wheel20, and hence of the hour and minute hands 4 and 6, is achieved.

Referring now to FIGS. 4 and 6, the signals from the timed signal sourceD may, as illustrated in FIG. 6A, comprise voltage pulses 30 eachcommencing at a time t and terminating at a time with an appropriateinterval between the ending of one pulse or signal 30 and the beginningof the next pulse or signal 30. As illustrated in FIG. 6A the timeinterval between t and t is considerably greater than that required toproduce a step movement of the output member of the mechanical drivemeans B which is operatively connected to the indicator means A (thearmature 8 of FIG. 2 or the pawl 22 of FIG. 3).

The input signal 30 is fed by lead 32 to the control means C, the lead32 connecting with a series capacitor 34 and a shunt resistor 36 whichdefine a ditferentiating network producing, as may be seen in FIG. 6B, aspike signal 38 in one sense at time t when the pulse 30 commences, anda spike signal 40 in the other sense at time t when the pulse 30disappears. The output of the differentiating circuit 34, 36 is fed bylead 42 to rectifier 44, the latter being poled so as to pass spikesignal 38 but block spike signal 40. The rectifier 44 is connected bylead 46 to the base of transistor 48. The emitter of transistor 48 isconnected to ground via resistor 50. The collector of transistor 48 isconnected to an energizing source or battery at terminal 52 via drivingcoil 14. The base of transistor 54 is connected by lead 56 to a point 58between the coil 14 and the collector of transistor 48. The emitter oftransistor 54 is connected by resistor 60 to the energizing sourceterminal 52. The collector of transistor 54 is connected by lead 62 tolead 46 and hence to the base of transistor 48.

The operation of the circuitry as thus far described is as follows: Whenan input pulse or signal 30 is first received, at time t the spikesignal 38 is formed by the differentiating circuit 34, 36, and thisspike signal passes through the rectifier 44 to the base of transistor48, turning the latter on, that is to say, making its collector-emitterpath conductive. As a result current flows through the driving coil 14in the output circuit of the transistor 48, energizing that driving coil14 and causing appropriate movement of the mechanical output member ofthe drive means B (here illustrated as the armature 8 in FIG. 2 or thepawl 22 in FIG. 3). As current flows through the driving coil 14 anappropriate bias is applied to the base of the transistor 54, causingthat transistor to become conductive. The collector-emitter currentpassing through transistor 54 serves to provide base current for thetransistor 48, keeping the latter in conductive condition. When thespike signal 38 disappears the transistor 48 thus is latched inconductive condition through the action of the transistor 54, and thedriving coil 14 remains energized, thus continuing to operatively actupon the output member (8 or 22) of the drive means B.

The cut-off means E is designed to terminate the energization of thedriving coil 14 as soon as the mechanical output member 8 or 22 hasmoved in a predetermined fashion. In the system shown in FIG. 4 thatpredetermined fashion constitutes movement until a predeterminedvelocity is attained. When the output member 8 or 22 moves in responseto energization of the driving coil 14, a part operatively connectedthereto moves with respect to the sensing coil 18, electromagneticallygenerating a signal therein, a typical such signal being shown in FIG.6C and represented by the line 64. This signal 64. is fed by lead 66 tothe base of transistor 68. The emitter of transistor 68 is connected toground by lead 70, and its collector is connected to lead 46 by lead 72.When the signal 64 reaches a predetermined magnitude, the system of FIG.4 being designed so that said predetermined magnitude is reached oncethe output member 8 or 22 has reached a predetermined velocity, thetransistor 68 will be turned on. Its emitter-collector output circuitwill then represent virtually a short circuit connection between lead 46and ground, thus operatively removing base current from the transistor48 and turning the latter olf, thereby de-energizing driving coil 14.With the de-energization of coil 14 transistor 54 is turned offand'hence transistor 48 is unlatched. When the signal 64 falls below theaforementioned predetermined value transistor 68 will turn off, but bythis time transistor 48 will have been unlatched and therefore it willremain off. The circuit will therefore be in stand-by condition,awaiting the receipt of the next signal pulse 30.

As may be seen from FIGS. 6A-E, the signal 64 reaches operative cut-offvalue at a time t which is located between t and 1 The energizingcurrent in coil 14, indicated at 74 in FIG. 6D, will therefore flow onlyfrom t to t and powered movement of the output member 8 or 22, and henceof the indicator means A, will likewise occur only between t and 1 asindicated at 76 in FIG. 6E.

The circuit of FIG. 5 is essentially the same as that of FIG. 4, butmodified so as to produce'cut-off of the energization of the drivingcoil 14 when the movement of the output member 8 or 22 has attained apredetermined position corresponding to that where the flux densityreaches a maximum value and reverses polarity i.e. the point of maximumcoincidence of the rotor tooth and pole piece 16. Hence the sensing coil18 in FIG. 5 is connected to the base of transistor 68 via adifferentiating network comprising series capacitor 78 and shuntresistor 80. As a result the biasing of the base of transistor 68 willbe determined by full coincidence between tooth 10 and pole piece 16,and hence by the position of the rotor 8. The circuit of FIG. 5 couldalso be used to control transistor 68 in accordance with acceleration ofthe rotor 8 if that should be appropriate.

From the above it will be seen that through the use of the presentinvention the driving coil 14 is powered only for so long as is requiredfor it to perform its assigned task, and no longer, and that this resultis achieved entirely independently of the duration of the initiatingsignal pulse 30. That pulse may, as specifically illustrated in FIG. 6,have a duration longer than that required to move the output member 8 or22 in predetermined fashion. Alternatively, the timing signal 30 mayhave a time duration less than that required to achieve predeterminedmovement of the output member 8 or 22; indeed, only a momentary signal,such as the spike signal 38, is needed to initiate each step of outputmovement. Hence the power source 52 must provide power only when thatpower is required to perform useful work. The effect in radicallyincreasing the effective life of the battery source for the powerprovided at terminal 52 will be obvious. In addition, the system willautomatically compensate for the effects of different ambient conditionson the readiness with which the output members 8 or 22 move. Moreover,by making the operation of the driving means B entirely independent ofthe duration of the signal from the souce D, greater latitude is providefor design for the signal source D.

The system of the present invention is of relatively wide applicability,and the specific electrically powered timing systems here disclosed arebut exemplary of many others in connection with which the system of thepresent invention has very advantageous results. Moreover, the specificmeans here disclosed to achieve the mechanical drive, the control andenergization thereof, and the cutoff of that energization, may also bewidely varied, the specific circuitry here disclosed being a simple andeffective embodiment which is, however, capable of extensivemodification. These and other variations may be made in the embodimentshere specifically disclosed, all without departing from the spirit ofthe invention as defined in the following claims.

We claim:

1. In an electric drive for a timepiece or the like which comprises asource of signals, a movable output member, moving means for moving saidoutput member in a predetermined fashion each time that a signal isreceived, and power means for energizing said moving means; theimprovement which comprises control means operatively connected betweensaid source and said power means and normally effective to cause saidpower means to energize said moving means upon the reception of a signalfrom said source and thereafter for a period of time in excess of thatrequired to cause said output member to move in said predeterminedfashion, sensing means operatively connected to said output member forsensing its motion and producing a cut-off signal when motion in saidpredetermined fashion has been achieved, and cut-off means operativelyconnected between said sensing means and said control means andeffective in response to said cut-off signal to cut off said controlmeans and terminate the energization of said moving means by said powermeans.

2. The electric drive of claim 1, in which said control means iseffective to cause said power means to energize said moving meanscontinuously once said signal from said source has been received untilsaid control means is operatively acted upon by said cut-off means.

3. The electric drive of claim 2, in which said predetermined fashion ofmovement of said output member comprises movement for a predetermineddistance.

4. The electric drive of claim 2, in which said predetermined fashion ofmovement of said output member comprises movement at a predeterminedvelocity.

5. The electric drive of claim 1, in which said signal source producessignals having a duration longer than that required to cause said outputmember to move in said predetermined fashion, said cut-off means beingeffective to override said signal and cut off said control means even inthe presence of said signal.

6. The electric drive of claim 5, in which said predetermined fashion ofmovement of said output member comprises movement for a predetermineddistance.

7. The electric drive of claim 5, in which said predetermined fashion ofmovement of said output member comprises movement at a predeterminedvelocity.

8. The electric drive of claim 1, in which said signal source producessignals having a duration longer than that required to cause said outputmember to move in said predetermined fashion, said cut-off means beingeffective to override said signal and cut off said control means even inthe presence of said signal, and means for thereafter preventingre-actuation of said control means until a new signal is received fromsaid source.

9. The electric drive of claim 8, in which said predetermined fashion ofmovement of said output member comprises movement for a predetermineddistance.

10. The electric drive of claim 8, in which said predetermined fashionof movement of said output member comprises movement at a predeterminedvelocity.

11. The electric drive of claim 1, in which said control means iseffective to cause said power means to energize said moving meanscontinuously once said signal from said source has been received untilsaid control means is operatively acted upon by said cut-off means, andin which said signal source produces signals having a duration longerthan that required to cause said output member to move in saidpredetermined fashion, said cut-off means being effective to overridesaid signal and cut off said control means even in the presence of saidsignal.

12. The electric drive of claim 11, in which said predetermined fashionof movement of said output member comprises movement for a predetermineddistance.

13. The electric drive of claim 11, in which said predetermined fashionof movement of said output member comprises movement at a predeterminedvelocity.

14. The electric drive of claim 1, in which said control means iseffective to cause said power means to energize said moving meanscontinuously once said signal from said source has been received untilsaid control means is operatively acted upon by said cut-off means, andin which said signal source produces signals having a duration longerthan that required to cause said output member to move in saidpredetermined fashion, said cutoff means being effective to overridesaid signal and cut off said control means even in the presence of saidsignal, and means for thereafter preventing re-actuation of said controlmeans until a new signal is received from said source.

15. The electric drive of claim 14, in which said predetermined fashionof movement of said output member comprises movement for a predetermineddistance.

16. The electric drive of claim 14, in which said predetermined fashionof movement of said output member comprises movement at a predeterminedvelocity.

17. The electric drive of claim 1, in which said control means comprisesfirst means for producing a control pulse from said signal from saidsource, a first control transistor normally in an off-condition andoperatively connected to said first means so as to be turned on by saidcontrol pulse, an output circuit for said first control transistoroperatively connected to said moving means, and latching meansoperatively connected between said output circuit and said first controltransistor and effective to maintain said first control transistor in anon-condition while operative current flows in said output circuit ofsaid first control transistor; said cutoif means comprising a secondcontrol transistor normally in an off-condition and operativelyconnected to said sensing means so as to be turned on when apredetermined signal is received from said sensing means, said secondcontrol transistor having an output circuit operatively connected tosaid first control transistor so as to turn the latter off when saidsecond control transistor is on, thereby stopping current flow in saidoutput circuit of said first control transistor and de-actuating saidlatching means.

18. The electric drive of claim 17, in which said sensing means producessaid predetermined signal when said output member has moved apredetermined distance.

19. The electric drive of claim 17, in which said sensing means producessaid predetermined signal when said output member is moving at apredetermined speed.

References Cited UNITED STATES PATENTS 3,042,847 7/ 196.2 Welch 318-2543,304, 48 1 2/ 1967 Saussele 318-138 3,329,852 7/1967 Saussele et al318-138 3,333,171 7/1967 Platnick 318-138 3,353,076 11/1967 Haines -1318-138 3,359,474 12/1967 Welch et al. 318-138 3,386,019 5/ 1968 Hill318-138 G. R. SIMMONS, Primary Examiner U.S. Cl. X.R.

